Rank: 4810 based on 18 downloads (last 30 days) and 1 file submitted
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Joel

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Washington University in St. Louis
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Physics and mathematics undergraduate student.


 

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22 Aug 2009 Speckle Size via Autocorrelation Outputs the size of speckles in an image that has a **uniform background**. Author: Joel autocorrelation, autocovariance, speckle, image processing 18 6
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Comments and Ratings by Joel
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07 Jul 2010 Speckle Size via Autocorrelation Outputs the size of speckles in an image that has a **uniform background**. Author: Joel

The units are just in 'pixels'. If you acquire the image with a camera you would have to find the dimensions of one pixel on your own, perhaps by using a reference (e.g. I know this object is 1.0cm long) or perhaps by some more complicated calculation if you use lenses to focus an image onto a digital camera. Manufacturers' datasheets give pixel sizes for most digital cameras, I believe, which would be one part of that calculation. It is true that without having a pixel-to-distance conversion the program doesn't help much.

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21 May 2012 Speckle Size via Autocorrelation Outputs the size of speckles in an image that has a **uniform background**. Author: Joel Surya Gnyawali

Hi Joel,

Can you please help me how proceed to play with your Speckle Size via autocorrelation. My question is do I have to make GUI.

Thanks for the help
Surya

09 Sep 2011 Speckle Size via Autocorrelation Outputs the size of speckles in an image that has a **uniform background**. Author: Joel Jens Munk Hansen

Hey Joel. I looked into your source and found that you have misunderstood how the correlation length can be obtained from the auto-covariance. You are using the FWHM of the fit. The correlation length is the value of the integral itself.

06 Jun 2011 Speckle Size via Autocorrelation Outputs the size of speckles in an image that has a **uniform background**. Author: Joel Ariel

Hello Joel,

Please disregard my last message.
(I just didn't install the Signal Process tool box)

Best,
Ariel

06 Jun 2011 Speckle Size via Autocorrelation Outputs the size of speckles in an image that has a **uniform background**. Author: Joel Ariel

Hello Joel,

I'm trying to run your function but for some reason i get this error:
% ??? Undefined function or method 'xcov' %for input arguments of type 'double'.

% Error in ==> SpeckleSize at 46
% s=size(xcov(E)); %finds the % size of the autocovariance array

Do you have any idea why do i get this error?

(P.S I'm using MATLAB2010B)

Thank you,
Ariel.

07 Jul 2010 Speckle Size via Autocorrelation Outputs the size of speckles in an image that has a **uniform background**. Author: Joel Joel

The units are just in 'pixels'. If you acquire the image with a camera you would have to find the dimensions of one pixel on your own, perhaps by using a reference (e.g. I know this object is 1.0cm long) or perhaps by some more complicated calculation if you use lenses to focus an image onto a digital camera. Manufacturers' datasheets give pixel sizes for most digital cameras, I believe, which would be one part of that calculation. It is true that without having a pixel-to-distance conversion the program doesn't help much.

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